Comparative Evaluation of Alumina, Hydroxyapatite, and Their Combination for Dental Enamel Cavity Cutting in an Air Abrasion System: An In Vitro <scp>SEM</scp> Study

Dental air abrasion is a minimally invasive technique using abrasive particles to remove carious tooth structure. Alumina particles, commonly preferred due to their cutting efficiency, pose toxicity risks if inhaled. This study evaluated hydroxyapatite (HA) and an alumina + HA combination as alternatives to alumina for enamel cutting efficiency. Extracted human third molars with sound enamel (N = 30) were divided into three groups: (1) alumina 29 μm (control), (2) HA, and (3) alumina + HA. Morphological analysis of powders and cavity cutting performance were assessed using scanning electron microscopy (SEM). Alumina particles were coarse and angular, HA particles were rounded, and alumina + HA showed mixed morphology on SEM analysis. Cavity cutting results showed alumina produced the deepest cavities (mean: 2.5 mm), followed by alumina + HA (mean: 2.12 mm) and HA alone (mean: 0.75 mm). Statistically significant differences were detected between alumina and HA (p = 0.0003) and alumina + HA and HA (p = 0.008), but no significant differences between alumina and alumina + HA (p > 0.99) were observed. SEM analysis of the shape of the cavities revealed cylindrical shapes for alumina and alumina + HA groups and conical shapes for the HA group. The alumina + HA combination demonstrated effective enamel cutting efficiency while the presence of HA could be potentially useful for remineralization, presenting a safer alternative to pure alumina. Further in vivo studies are recommended to validate these findings.